I'm a beginner and I'm having trouble understanding/using texture mapping. Below is the code for a sphere (from the Red Book). I simply want to color part of the sphere a differnt color. I'm trying to paint an eye. Do I need to use texture mapping? I've been trying to learn texture mapping, but I don't see how to do what I want. Would you please add the code needed to the folling program. Thank you.

/*
* light.c
* This program demonstrates the use of the OpenGL lighting
* model. A sphere is drawn using a grey material characteristic.
* A single light source illuminates the object.
*/
#include <GL/glut.h>
#include <stdlib.h>